Production of a cellulose staple fiber batting



PRODUCTION OF A CELLULOSE STAPLE FIBER BATTING Edward T. Powers, Old Greenwich, Conn., assignor to Celanese Corporation of America, New York, NY, a corporation of Delaware Filed Oct. 7, 1955, Ser. No. 539,291

6 Claims. (CI. 28-76) This invention relates to batting and relates more particularly to a batting of cellulose staple fibers having a strong, coherent structure.

An important object of this invention is to provide a novel batting of cellulose staple fibers having a strong, coherent structure which will be suited for a wide variety of uses.

A further object of this invention is to provide a novel glrjocess for the production of a batting of cellulose staple ers.

Other objects of this invention will be apparent from the following detailed description and claims.

According to the present invention, there is formed a batting of staple fibers of an organic derivative of cellulose, such as cellulose acetate, in which, the individual fibers are interlocked with one another. The said batting is then treated with a saponifying agent to convert the cellulose acetate to cellulose, during which process there is a considerable shrinkage of the batting. There is obtained in this way a batting of cellulose staple fibers having a considerable tensile strength and a relatively high density. The properties of this batting are in many ways similar to those of a wool felt so that it can replace wool felt in such uses as apparel, including hats, skirts, sportswear and the like. It can also be used for industrial purposes such as pads for machinery, lamps and other articles. The batting prepared in accordance with this invention is also suited for use as a gasketing and filtering material.

The initial batting may be made by any desired method, of which there are many known in the art. For example, fibers of a suitable length may be suspended in a stream of fluid, such as air or water, and deposited from said stream on a surface through which the fluid can flow such as a belt pervious to said fluid, a foramino-us member, or the like. Alternatively, the staple fibers may be converted into a batting by means of a carding machine. The staple fibers going into it the batting may have a denier ranging from about 1, or less, to 30, or more, and may range in length from about 1 inch, or less, to 6 inches, or more. The staple fibers may be straight, but preferably have a crimp therein so that they will cling together more readily during the production of the initial batting.

The staple fibers in the batting are interlocked with one another. A preferred way of achieving such interlocking is by treating the batting to cause the fibers to become tangled with one another so that they cannot be readily separated without tearing the individual fibers. This may be readily achieved by needling the initial batting.

The staple fibers in the batting may also be interlocked with one another through the use of a suitable bonding agent. Examples of bonding agents that may be used for this purpose are butadiene polymers and copolymers, melamine resins, styrene copolymers and ureaformaldehyde resins. These bonding agents or a solution thereof in a suitable solvent, may be sprayed on or Patent 9 mixed with the staple fibers during the production of the batting or may be sprayed onto or otherwise applied to the batting after it has been formed. The batting may then be treated as by heating or the like to drive off the solvent and thereby produce the desired bond between the individual staple fibers at the points where such fibers contact one another.

Another way in which the staple fibers in the batting may be interlocked with one another is through the potential adhesiveness of the organic acid esters of cellulose of which said staple fibers are composed. Thus,

there may be applied to the batting a solvent or plasticizing agent for the organic acid ester of cellulose, such as acetone, methylene chloride, or the like, to cause the softening of the organic acid ester of cellulose and the coalescence of the fibers at their points of contact, following which, if desired, the solvent or plasticizing agent maybe driven ofi from the batting by means of a stream of evaporative medium. The coalescence of the staple fibers through the use of a solvent or plasticizing agent may be accelerated by subjecting said batting to heat, pressure or both. It is also possible to subject the batting to the action of heat and, if desired, pres-sure whereby the heat itself will cause a softening of the organic acid ester of cellulose and a coalescence of the staple fibers at their points of contact. The action of the heat may be accelerated and lower temperatures made effective if there is incorporated into or applied to the staple fibers a plasticizing agent or latent solvent for the organic acid ester of cellulose.

The batting is then treated with a saponifying agent to convert the organic acid ester of cellulose to cellulose. The saponifying agent may comprise an aqueous or alcoholic solution of a suitable alkaline material such as sodium hydroxide or potassium hydroxide. There may also be present in the said solution a bufiering agent such as sodium acetate, potassium acetate, or the like to control and make more complete the action of the saponifying agent. During the saponification, the organic acid ester of cellulose staple fibers shrink to a considerable extent, due to the reduction in the volume of the said fibers as they are converted to cellulose and also to the shrinkage of the cellulose fibers under the influence of the alkaline solution. This shrinkage greatly increases the density of the batting. It also increases the degree of interlocking of the staple fibers, particularly where such interlocking has been effected through the mechanical tangling of the fibers. As a result, the batting shows a considerable improvement in strength which increases its suitability for many applications where it will be subjected to rough handling. The saponification of the batting may be carried out on a batch basis by immersing said batting in a vat or the like containing the sapo'nifying agent. It is preferred, however, to carry out the saponification in a continuous manner by passing the batting into, through and out of a vat or the like containing the saponifying agent, the rate of movement of the batting being such as to effect the saponification of the organic acid ester of cellulose. Following the saponification, the batting is advantageously washed to remove therefrom the excess saponifying agent and the salts produced by the saponification, and is finally dried.

Before the batting is treated with a saponifying agent, it may, if desired, be shaped to form a three-dimensional structure. The shaping may be carried out in any desired manner and may beassisted through the use of heat and pressure. In this way, it is possible readily to produce a product of any desired structure.

The process of this invention will now be described specifically in connection with a batting of staple fibers of cellulose acetate which is commercially the most important organic acid ester of cellulose at the present time. It may, however, also be used with staple fibers of other organic acid esters of cellulose, including, for example, cellulose propionate, cellulose butyrate, cellulose acetate propionate and cellulose acetate butyrate. There may also be present in the batting a proportion of other fibers such as cotton, rayon, glass or the like.

The following example is given to illustrate this invention further.

Example A batting formed of 12 denier per filament cellulose acetate staple fibers 2 inches long, having a density of 0.46 lb. per cubic foot and a thickness of 2 inches, is passed through a needling machine to produce a batting having a density of 3.68 lbs. per cubic foot and a thickness of inch. The needled batting is then entered into an aqueous bath containing 35% by weight of sodium hydroxide and maintained at 60 C. After three minutes, the batting is removed from the aqueous bath, washed thoroughly with water and dried in a vertically suspended position for 24 hours in a room with a temperature of 70 F, and a relative humidity of 65%. The batting obtained in this manner resembles a Wool felt, has a density of 13.5 lbs. per cubic foot.' It has a high strength as compared with the original batting and is well suited for a wide variety of applications.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of a batting of cellulose staple fibers, which comprises treating a batting consisti ing essentially of mechanically interlocked organic acid ester of cellulose staple fibers with a saponifying agent to convert the fibers to cellulose fibers, said treatment converting said batting to a material similar to wool felt.

2. Process for the production of a batting of cellulose staple fibers, which comprises forming a batting consisting essentially of mechanically interlocked organic acid ester of cellulose staple fibers, and treating said batting with a saponifying agent to convert the fibers to cellulose fibers.

3. Process for the production of a batting of cellulose staple fibers, which comprises forming a batting consisting essentially of organic acid ester of cellulose staple fibers, needling the batting to interlock the fibers therein mechanically, and treating said batting with a saponifying agent to convert the fibers to cellulose fibers.

4. Process for the production of a batting of cellulose staple fibers, which comprises treating a batting consisting essentially of mechanically interlocked cellulose acetate staple fibers with a saponifying agent to convert the fibers to cellulose fibers.

5. Process for the production of a batting of cellulose staple fibers; which comprises forming a batting consisting essentially of cellulose acetate staple fibers, needling the batting to interlock the fibers therein mechanically, and treating said batting with a saponifying agent to convert the fibers to cellulose fibers.

6. Batting produced by the process of claim 3.

References Cited in the file of this patent UNITED STATES PATENTS 1,966,440 Dickie et a1. July 17, 1934 2,118,840 Dreyfus May 31, 1938 2,198,660 Dreyfus Apr. 30, 1940 2,357,392 Francis Sept. 5, 1944 2,437,689 Francis Mar. 16, 1948 2,538,899 Dodge et a1 Jan. 23, 1951 2,647,297 Battista Aug. 4, 1953 2,774,126 Secrist Dec. 18, 1956 2,774,129 Secrist Dec. 18, 1956 

1. PROCESS FOR THE PRODUCTION OF A BATTING OF CELLULOSE STAPLE FIBERS, WHICH COMPRISES TREATING A BATTING CONSISTING ESSENTIALLY OF MECHANICALLY INTERLOCKED ORGANIC ACID ESTER OF CELLULOSE STAPLE FIBERS WITH A SAPONIFYING AGENT TO CONVERT THE FIBERS TO CELLULOSE FIBERS, SAID TREATMENT CONVERTING SAID BATTING TO A MATERIAL SIMILAR TO WOOL FELT. 